After forging, austenitic stainless steel must be treated to develop the desired physical and mechanical properties, such as strength or hardness. Strength is given to steel by stressing it which causes local areas of strain. In general, stress can be caused by (1) mechanically working the steel, such as by cold-working, to cause a decrease in grain size or (2) heat treating the steel from above the lower critical temperature to cause structural transformations in the steel. Austenitic stainless steel, however, is not hardenable by heat treatment and typically must be cold-worked to develop mechanical and physical properties.
Inherent in the cold-working process, however, are problems of noise control and metallurgical control. The cold-working process is very noisy, typically involving a steam hammer constantly pounding a workpiece. In addition, the mechanical and physical properties of the workpiece are dependent on the amount of cold-working. The amount of cold-working required to achieve particular properties is difficult to control. Too much cold-working can lead to irreversible damage to a workpiece by making it too hard and decreasing its corrosion-resistance. In addition, insufficient cold-working will not give desired properties and requires rework of the material resulting in undue delays in processing.